This invention relates generally to the field of machinery joint packing or fluid sealing members and more specifically to an improved U-shaped composite packing ring seal and a method for making same.
"U" type ring seals are for use in sealing dynamic and static hydraulic or gas applications for prevention of internal and external leakage. "U" type seals are pressure energized with pressure against the open end of the "U" acting equally on the inner surface in all directions, statically balancing the seal. U-seals are normally assembled with an interference fit with the width dimension between sealing lips being most critical especially in dynamic machinery joint packing applications. This interference fit of the sealing lips must provide for good sealing which will withstand frictional wear problems.
In the past multiple part "U" type seals have found great usage due to their ability to provide the desired ultimate sealing properties. Seals of this type are, for example, illustrated and described in U.S. Pat. No. 3,342,500 to C. B. Knudson and U.S. Pat. No. 3,653,672 to Maurice D. Felt. These prior art seals due to their multipart, nonintegral construction, however, can lead to sealing reliability problems. The separately formed parts of this ultimate seal construction all have manufacturing tolerances which in the aggregate can easily produce wide variations in the critical sealing dimensions from seal to seal which in turn gives rise to sealing problems in machinery joint packing use. That is, the outer U-shaped packing ring and the internal insert member both have manufacturing tolerances which when combined with finish operation variations can lead to standard size seals with wide variations of critical dimensions.
Additionally, many seals of various sizes are needed for the numerous machinery joint packing applications which necessitates the need for manufacture and accurate inventory of many components many of which can be nearly the same size. Efforts have to be made to insure individual component parts of the seal and especially the internal member are not mixed together or mistaken one for another. Lastly, the use of the multipart construction which is not integrally formed together necessitates final assembly operations and the costs associated with them.
Accordingly, it is an object of the present invention to provide a novel sealing ring member which is rugged, effective and reliable in use and simple in design and economical to manufacture.
It is another object of this invention to provide an integrally formed composite sealing ring.
It is another object of this invention to provide an integrally formed U-shaped composite sealing ring.
It is yet another object of this invention to provide a method for producing an integrally formed composite sealing ring with high reproducibility sealing ring to sealing ring.
It is still another object of the invention to provide a method for producing an integrally formed U-shaped composite sealing ring which is reliable in use and economical to manufacture.
These and other objects of the invention will become apparent to those skilled in the art from a reading of the following specification and claims.
Briefly the foregoing objects are accomplished by providing U-shaped composite packing ring seal including a U-shaped shell member and an actuator member formed in situ in which the shell member has in transverse cross section a base portion with two legs extending from the base to form a cavity therebetween. This cavity is filled with liquid elastomer which is cured in situ to form the actuator portion of seal. This integrally formed U-shaped composite ring seal yields a highly reliable seal with minimal dimensional variation problems. Also this seal is easy and economical to manufacture.
The invention also includes the provision of a method for making a U-shaped composite ring seal including: forming a U-shaped shell having a base, two legs extending from the base and a cavity between the legs; filling the cavity with a liquid material which forms a substantially incompressible elastomer material when cured; curing said material and moving a cutting tool along a predetermined path to remove a portion of said legs and said material thereby providing for the sealing lips of the seal. This method of integral seal construction does away with final seal assembly operations and the costs associated with them. Also by varying the cutting angle calibration adjustments can be made in critical lip seal dimension in the as assembled state.